The graphical user interface (GUI) has become the standard paradigm for human interaction with personal computers. A GUI consists of a screen for displaying graphical elements and a pointing device for pointing at and selecting these elements. One of the most standard of GUI graphical elements is the scrollbar. Scrollbars are used for bringing particular sections of a large document into view on a display screen that is too small to view the entire document at once. Almost all programs for navigating documents incorporate a vertical scrollbar and most contain a horizontal scrollbar.
Although scrollbars have become the standard mechanism for navigating large documents, using them requires a significant level of attention and dexterity. And since scrolling is such a commonly performed function, newer systems have incorporated schemes for affecting scrolling without the need for visual interaction with scrollbars. The most widely deployed device for easing the scrolling task is the wheel mouse. The wheel mouse augments the pointing function of the standard computer mouse with a detented wheel typically mounted between the left and right buttons. Most current GUI systems will use the signals produced by rotation of this wheel to vertically scroll the document with the current keyboard focus or the document lying under the display cursor.
One problem with a typical mouse wheel, of course, is that only vertical scrolling is supported. Another problem with the scheme is that in the typical configuration, the wheel can only be slowly rotated, making it marginally useful for scrolling large distances. Lastly, portable systems often incorporate pointing devices other than a mouse so a more universal scrolling acceleration mechanism is desirable.
Various attempts have been made to perform scrolling functions using a touchpad-type device. One technique, for example, uses a touchpad to perform both pointing and “virtual” scrolling functions using regions at the right and bottom of the pad dedicated to vertical and horizontal scrolling, respectively. When a finger lands in one of the scrolling regions and stays within that region, special software generates scrolling information instead of the normal pointing information. Pointing functionality is restored by moving the finger out of the scrolling region with or without an intervening lifting of the finger from the pad. An exemplary implementation of scrolling performed on a touchpad device is described in U.S. Pat. No. 5,943,052.
Touchpad virtual scrolling is a fairly natural solution to the problem of easing both vertical and horizontal scrolling but it frequently suffers from the same problem as the wheel mouse, in that scrolling large distances can be inefficient. One way of alleviating this problem, called coasting, attempts to remedy this issue. Typically, a user activates a coasting feature by initiating scrolling and then having the finger leave the pad while the finger velocity parallel to the scrolling region is still high. When coasting is activated, the touchpad subsystem typically generates a continuous stream of scrolling signals which is interruptible by again touching the pad. U.S. Pat. No. 5,943,052 also shows an exemplary coasting implementation.
While coasting can be used to scroll long distances fairly quickly, many implementations can require considerable dexterity to use efficiently. Further, each user typically adjusts the coasting rate to match their personal preference, and any such preference might only work well for some document types.
Another technique for scrolling uses a portion of a pen-type touchpad as a “jog dial” where pen motion around the center of the dial is used to generate scrolling signals. Typically, the rate of generation of scrolling signals is proportional to the rate of angle subtended by the pen as it moves around the center of the dial. A further refinement allows the center point used in the subtended angle calculation to move and thereby follow freeform circular pen motions.
Jog dial scrolling can be a significant improvement over a mouse wheel or touchpad virtual scrolling for moving large distances within a document. However, the idea of a jog dial is conceptually distinct from that of a linear scroll bar and therefore training naïve users in its use is non-trivial. The particular embodiment described in the jog-dial patent placed the touchpad over a display screen so that the jog-dial could be displayed under the pad.
Touchpad virtual scrolling is a good conceptual mapping between GUI scrollbars and the dedicated touchpad present in the majority of today's portable computers. While the jog dial provides some benefits over current touchpad scrolling implementations, the jog dial is conceptually distinct from linear scrollbars, and can therefore require significant acclimation for naive users. What is therefore needed is a method and a system for generating scrolling signals that is conceptually compatible with linear scrollbars but that provides improved sensitivity and dynamic range. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawing figures and the foregoing technical field and background.